Minor improvements

This new release fixes two issues:

• At every new execution, clear potentially conflicting global variables (which may have been created inside 'STRIKE_GOLDD.m' in previous executions of the algorithm).
• Modification of the 'elim_and_recalc' and the main 'STRIKE_GOLDD' scripts, in order to avoid unnecessary calculations of the observability rank. In the previous version this could happen when analysing a model with unmeasured inputs ('w'); when adding new Lie derivatives and recalculating the rank for each variable (parameter/state/input), the knowledge about which variables had already been classified as observable was not exploited.

Implementation of the ORC-DF algorithm and multiexperiment support

STRIKE-GOLDD v2.2 includes an implementation of the ORC-DF algorithm presented in [1]. This method provides an additional way of analysing the observability of nonlinear systems that are affine in the inputs.

Furthermore, STRIKE-GOLDD v2.2 provides support for the observability analysis with multiple experiments, by enabling the automatic reformulation of a model for a multi-experiment setting.

The new features of STIKE-GOLDD v2.2, including a comparison between STRIKE-GOLDD's core algorithm and ORC-DF, are described in [2].

[1] K. Maes, M.N. Chatzis, G. Lombaert. "Observability of nonlinear systems with unmeasured inputs". Mechanical Systems and Signal Processing, 130:378-394, 2019. doi:10.1016/j.ymssp.2019.05.010
[2] N. Martínez, A.F. Villaverde. "Nonlinear observability algorithms with known and unknown inputs: analysis and implementation". arxiv preprint.

Calculation of Lie symmetries

The main novelty in STRIKE-GOLDD release v2.1.6 is the addition of code for finding Lie symmetries and for calculating symmetry-breaking transformations.

Furthermore, a number of bugs have been fixed since the last official release (v2.1.2). These bugs appeared in:

• some calculations of Lie derivatives (fixed in v2.1.4).
• occasional dimension mismatch errors when using decomposition (fixed in v2.1.5).
• numeric calculation of the rank when there are parameters that appear only in the output function (fixed in this release, v2.1.6).

2.1.2: More consistent stopping criterion

Stop as soon as the model is classified as FISPO, even if some time derivatives of the unknown input have not been classified as observable.

New version 2.1.1 of STRIKE-GOLDD

v2.1.1

removed deprecated functions

First release of STRIKE-GOLDD 2.1

This is the first release of the 2.1 version.